LED with Reduced Electrode Area

Abstract

A light source and method for fabricating the same are disclosed. The light source includes a substrate and first and second semiconductor layers that surround an active layer. The first layer includes a material of a first conductivity type adjacent to the substrate. The active layer overlies the first layer and generates light when holes and electrons recombine therein. The second layer includes a material of a second conductivity type overlying the active layer, the second layer having a first surface overlying the active layer and a second surface opposite to the first surface. A trench extends through the second layer and the active layer into the first layer. The trench has electrically insulating walls. A first electrode is disposed in the trench such that the first electrode is in electrical contact with the first layer, and the second electrode is in electrical contact with the second layer.

1 . A light source comprising:
 a substrate;   a first layer comprising a material of a first conductivity type adjacent to said substrate;   an active layer overlying said first layer, said active layer generating light when holes and electrons recombine therein;   a second layer comprising a material of a second conductivity type overlying said active layer, said second layer having a first surface overlying said active layer and a second surface opposite to said first surface;   a trench extending through said second layer and said active layer into said first layer, said trench having electrically insulating walls;   a first electrode disposed in said trench such that said first electrode is in electrical contact with said first layer; and   a second electrode in electrical contact with said second layer.   wherein said light source is fabricated in a fabrication process characterized by an alignment tolerance that specifies a magnitude of alignment errors in depositing said first electrode in said trench and wherein said insulating walls have a thickness less than said alignment errors.   
     
     
         2 . The light source of  claim 1  wherein said electrically insulating walls comprise a layer of SiN. 
     
     
         3 . The light source of  claim 1  wherein said first electrode comprises a layer of metal that fills said trench and is in contact with said insulating walls. 
     
     
         4 . The light source of  claim 1  further comprising a layer of transparent electrically conducting material between said second electrode and said second surface. 
     
     
         5 . The light source of  claim 4  further comprising an electrical insulator underlying said second electrical contact and disposed between said layer of transparent electrically conducting material and said second surface. 
     
     
         6 . The light source of  claim 5  wherein said electrically insulating walls comprise a layer of an insulating material and said insulator comprises the same insulating material. 
     
     
         7 . The light source of  claim 6  wherein said insulating material is chosen from the group consisting of SiN, AlNx, TiOx, AlOx, and SiOxNy. 
     
     
         8 . A method for fabricating a light emitting device, said method comprising:
 depositing a first layer comprising a material of a first conductivity type adjacent to a substrate;   depositing an active layer overlying said first layer, said active layer generating light when holes and electrons recombine therein;   depositing a second layer comprising a material of a second conductivity type overlying said active layer, said second layer having a first surface overlying said active layer and a second surface opposite to said first surface;   etching a trench extending through said second layer and said active layer into said first layer;   depositing an insulating material in said trench;   etching a hole in said insulating layer in a portion of said insulating layer to expose a portion of said first layer with said trench; and   depositing a layer of conducting material in said trench to form a first contact that is electrically connected to said first layer.   
     
     
         9 . The method of  claim 8  further comprising depositing said insulating material on said second surface at the same time that said insulating layer is deposited into said trench and patterning said insulating material to form an island of insulating material adjacent to said second surface. 
     
     
         10 . The method of  claim 9  further comprising depositing a transparent layer of electrically conducting material over said island and said second surface and then depositing a patterned layer of electrically conducting material over said island to form a second contact that is electrically connected to said transparent layer.